How to set the type for variables block in azure data factory pipeline?

Terraform Providers Azure
1

On the data_factory_pipeline, how to set the type for pipeline variables. In the example given at the below link, it has only string value. Something like this :

 variables = {
    "bob" = "item1"
  }

https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/data_factory_pipeline

Tried variable definition given here : Customize Terraform Configuration with Variables | Terraform - HashiCorp Learn. But, it didn’t work.

Any ideas ? Thanks for the help in advance.